Persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCB) have the volatile migration, are present in a wide range of the concentration in various environmental media, are known as a material influencing on the human body, and PCB is required to be removed and rendered harmless. In order to effectively treat persistent organic pollutants having the characteristics)by a combusting method and a chemical treating method, it becomes important to selectively separate and recover only persistent organic pollutants from environmental media in which those pollutants are present. In particular, in treatment of organic pollutants present in waste oils such as fats and oils at the low concentration of ppm order, since it is difficult to selectively separate and recover organic pollutants having the high affinity with media, a substantial amount of pollutants to be used becomes immense, being extremely ineffective from a viewpoint of energy.
Previously, as a method of selectively separating and recovering organic pollutants which are lipophilic materials from fats and oils contaminated with organic pollutants, an evaporating method and a liquid-liquid extracting method are widely used.
This evaporating method utilizes a difference in boiling points of 2 or more materials in order to separate a mixture of those materials as is well known. However, since, in mineral oils which are fats and oils to be treated have boiling points close to those of aromatic halogenated compounds which are representative pollutants, it is difficult to recover aromatic halogenated compounds from fats and oils at a high precision.
In addition, a liquid-liquid extracting method is to separate and remove pollutants by transferring pollutants from fat and oils into non-protonic polar solvents by a first step of extracting aromatic halogenated compounds or pollutants dissolved in fats and oils (liquid) into non-protonic polar solvents, and a second step of separating fats and oils and non-protonic polar solvents containing the extracted aromatic halogenated compounds, for example, disclosed in U.S. Pat. No. 4,405,448.
However, in the second step, since two liquids can not be separated simply, there is a problem that an amount of aromatic halogenated compounds-remaining fats and oils becomes large, fats and oils are mixed into separated non-protonic polar solvents, and it is difficult to perform separating treatment at a high precision.